
Hexanoic acid derived statins of general formula (1) or salts thereof inhibit the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) and are thus useful as a hypolipidemic and hypocholesterolemic agents. Examples of these statins are cerivastatin wherein R1 is a radical of formula (C), fluvastatin wherein R1 is a radical of formula (F), pitavastatin wherein R1 is a radical of formula (P) and rosuvastatin wherein R1 is a radical of formula (R).

For the introduction of the chiral part of the abovementioned molecules, intermediates of general formula (2) play a pivotal role.

In the compounds of general formula (2) R2 and R3 each independently stand for an alkyl with for instance 1 to 12 carbon atoms and R2 and R3 may form a ring together with the carbon atom to which they are bound. The group R4 is a carboxylic acid protecting group. For preparative purposes, R4 must be a group that can be easily removed after formation of the statin structure. Suitable groups in this respect have proven to be sec-butyl, tert-butyl, iso-propyl and the like. R5 is an aryl group that is suitable for a one-pot or modified Julia-Kocienski olefination, examples of which are tetrazole-based groups and substituted phenyl and benzimidazole type compounds (e.g. P. R. Blakemore, J. Chem. Soc., Perkin Trans. 1, 2002, 2563). For the purpose of this olefination the compound of general formula (2) is oxidized to the sulfone of general formula (3).

A method for preparing chiral diol sulfones is described in WO 2002/098854 and WO 2001/096311. In these citations, a sulfone is prepared from an alcohol, more in particular tert-butyl 2-((4R,6S)-6-(hydroxymethyl)-2,2-dimethyl-1,3-dioxan-4-yl)acetate known as “Kaneka alcohol”. The preparation of such an alcohol is described in EP 1024139. The synthesis in the prior art has several disadvantages, the most prominent being that many reaction steps are required and that trifluoromethanesulfonic anhydride or another sulfonic acid derived activating agent is used to activate the alcohol function to an extent that a nucleophilic attack with a thiol is possible. Trifluoromethanesulfonic anhydride is an extremely hazardous and expensive component, which causes costly work-up procedures due to environmentally problematic waste streams. It is an object of the present invention to provide a process, in which not only the use of an activating agent like trifluoromethanesulfonic anhydride is omitted but which also reduces the number of chemical conversions required.